Modern automotive paint shops include a continuous process during which vehicle bodies are painted while traveling along a conveyor through a paint booth. While advances in technology have improved the transfer of particulate paint atomized by paint guns to these vehicle bodies, a substantial amount of particulate paint does not adhere to these vehicle bodies and can remain airborne within the paint booth. The resulting effect of these airborne particles that have not adhered to the desired vehicle body includes paint defects, particularly when an airborne particle from a first color lands upon a subsequent vehicle being painted with a second color. If these particles remain airborne within the paint booth, the booth itself can become coated with the paint particles. Further, the airborne paint particles can present a health hazard to workers that are required to be in the booth during the painting process.
In order to maintain a clean environment within the paint booth, a continuous downflow of air is maintained within the booth to force the paint particles through openings in the booth floor thereby removing these paint particles, and any other airborne contaminants, from the paint booth. In order to prevent these airborne paint particles from adhering to the booth and to the equipment that generates the downward flow of air within the booth, a sheet of water constantly flows along a flood pan disposed beneath the paint booth floor. A significant percentage of paint particles are captured by this sheet of water, which includes a chemical solution capable of detackifying the paint particles and causing the paint particles to coagulate for subsequent filtration from the water flowing along a flood pan.
The water flowing along the flood pan, and the air flowing downward from the paint booth, which still contains airborne paint particles, travels through a scrubber extending downwardly from the flood pan. One such example of a scrubber is disclosed in U.S. Pat. No. 5,100,442, filed Mar. 31, 1992, the contents of which are incorporated into this application by reference. The scrubber causes the water flowing from the flood pan to remove paint particles from the air simultaneously flowing through the scrubber with the water.
The scrubber includes a constricted outlet that causes the water to be broken up into droplets. Because the droplets are relatively large, typically on an order of 100 micrometers, a significant amount of time relative to the flow of water and air is taken for the water to accelerate to the full speed of the air flowing through the scrubber. Because the paint particles are relatively small, on the order of 1-10 micrometers, the paint particles accelerate to the full air speed in a much shorter period of time relative to the water droplets. The interaction between the water droplets and the paint particles results in a collision causing the particles to be absorbed by the water droplets. As the water droplets and air move further away from the outlet, the ability of the water droplets to scrub the paint particles from the flow of air is reduced because the speed of the water droplets and the paint particles converge. Therefore, paint particles that have not been scrubbed from the flow of air flowing through the scrubber are known to adhere to the apparatus and ductwork that maintains the flow of air through the paint booth resulting in costly and time consuming cleaning maintenance. It is believed that the ability to scrub paint particles from the air reduces significantly as distance increases from the scrubber outlet.
Efforts to improve the scrubbing efficiency of these scrubbers have required an increase in pressure drop of the air flowing through the scrubber by forcing the air to travel through restrictions in the scrubber. Increases in pressure drop result in increases in the level of noise inside the paint booth and the surrounding areas adjacent the paint booth. Further, increasing the pressure drop in a scrubber assembly requires a significant increase in energy usage. Accordingly, attempts have been made to improve the scrubbing efficiency of scrubbers of this type without having to significantly increase the pressure drop of the air flowing through the booth.
The present invention is a scrubber assembly for removing particulate paint from a flow of air through a paint application booth. A sheet of water received from a water source flows across a flood pan disposed beneath the paint application booth. A separation chamber receives air and particulate paint from the paint application booth and water from the flood pan. A first and a second scrubber extend downwardly from the flood pan into the separation chamber fluidly connecting the paint booths and the separation chamber.
Each scrubber includes an inlet receiving air and particulate paint from the application booth and water from the flood pan. The first scrubber includes a first outlet discharging a first stream of air particulate paint and water received from the first inlet. A second scrubber includes a second outlet discharging a second stream of air particulate paint and water received from the second inlet. The first and second streams intersect within the separation chamber redirecting the direction of the streams exiting the scrubbers within the separation chamber.
At the location where the water droplets from each scrubber contacts the air stream from the opposing scrubber, the relative velocity is the sum of the drop in velocity and the air velocity. The relative velocity can be up to double the peak relative velocity that the water droplets experience during their initial acceleration through each outlet. The result is an additional scrubbing action that provides the ability to reduce the pressure drop of the flow of air through the scrubbers and still obtain an equivalent scrubbing efficiency yielded by a conventional scrubber assembly. Therefore, the noise level can be reduced within the paint booth and adjacent areas while not having to sacrifice scrubbing efficiency.